Remove explicit calls to computeRequirementSignature

We can rely on lazy calls to getRequirementSignature instead.

Author: xymus

lib/AST/GenericSignature.cpp

@@ -771,11 +771,6 @@ static bool hasNonCanonicalSelfProtocolRequirement(
     // If we don't already have a requirement signature for this protocol,
     // build one now.
     auto inProto = source->getProtocolDecl();
-    if (!inProto->isRequirementSignatureComputed()) {
-      inProto->computeRequirementSignature();
-      assert(inProto->isRequirementSignatureComputed() &&
-             "couldn't compute requirement signature?");
-    }
 
     // Check whether the given requirement is in the requirement signature.
     if (!source->usesRequirementSignature &&
@@ -856,13 +851,9 @@ void GenericSignature::buildConformanceAccessPath(
 
       // The generic signature builder we're using for this protocol
       // wasn't built from its own requirement signature, so we can't
-      // trust it. Make sure we have a requirement signature, then build
-      // a new generic signature builder.
+      // trust it, build a new generic signature builder.
       // FIXME: It would be better if we could replace the canonical generic
       // signature builder with the rebuilt one.
-      if (!requirementSignatureProto->isRequirementSignatureComputed())
-        requirementSignatureProto->computeRequirementSignature();
-      assert(requirementSignatureProto->isRequirementSignatureComputed());
 
       replacementBuilder.emplace(getASTContext());
       replacementBuilder->addGenericSignature(

lib/ClangImporter/ImportDecl.cpp

@@ -4521,10 +4521,6 @@ namespace {
                           inheritedTypes);
       result->setInherited(Impl.SwiftContext.AllocateCopy(inheritedTypes));
 
-      // Compute the requirement signature.
-      if (!result->isRequirementSignatureComputed())
-        result->computeRequirementSignature();
-
       result->setMemberLoader(&Impl, 0);
 
       // Add the protocol decl to ExternalDefinitions so that IRGen can emit
@@ -7878,9 +7874,6 @@ void ClangImporter::Implementation::finishNormalConformance(
   PrettyStackTraceConformance trace(SwiftContext, "completing import of",
                                     conformance);
 
-  if (!proto->isRequirementSignatureComputed())
-    proto->computeRequirementSignature();
-
   finishTypeWitnesses(conformance);
   finishInheritedConformances(conformance);
   finishSignatureConformances(conformance);

lib/Sema/TypeCheckGeneric.cpp

@@ -729,10 +729,8 @@ GenericEnvironment *TypeChecker::checkGenericEnvironment(
 
 void TypeChecker::validateGenericTypeSignature(GenericTypeDecl *typeDecl) {
   if (auto *proto = dyn_cast<ProtocolDecl>(typeDecl)) {
-    // Compute the requirement signature first.
-    if (!proto->isRequirementSignatureComputed())
-      proto->computeRequirementSignature();
-
+    // The requirement signature is created lazily by
+    // ProtocolDecl::getRequirementSignature().
     // The generic signature and environment is created lazily by
     // GenericContext::getGenericSignature(), so there is nothing we
     // need to do.